The plate on the top of the unit is an access door to get to the two 12AU7 vacuum tubes — just press the icon on the plate that looks like a hand and the whole just pivot up.
Some features from the website:
Constant Current: Very few preamplifiers use a constant current circuit. Backert Labs chose to keep the current on your tubes constant at all times. This is easier on them, allowing your tubes to last longer. (You’ve heard of amps that are “hard on tubes” — this refers to higher voltage and current running through the tubes.) Constant current also results in more linear amplification, or put simply, more accurate sound.
Active Management: (1) optimizes the preamp to work best with each specific tube you insert, (2) continually monitors and adjusts the circuit to match the needs of your tubes, as they age and gradually require different operating parameters, and (3) stabilizes tube bias in real-time by continuously negating the “bias tugging” effects caused by playing music.
- Active Management means that your Rhythm 1.1 will automatically adjust the bias of your tubes, continuously.
- Just bought a new pair of NOS tubes? Once you put them in, the bias is immediately adjusted specifically for them.
- Using the same tubes for 10 years? Bias will need adjustment as they age. Active Management does that.
- Playing music? In other preamplifiers, the bias will be changing constantly, in real time, due to the music signal itself — but Active Management negates this effect, allowing your tubes to run at a constant, smooth and correct bias.
Active Output Correction: (1) monitors and continually corrects the preamp’s output to adjust it back to the immediate, pure signal output of the tubes, (2) negates the harmful effects of interconnect inductance and capacitance, and (3) corrects the preamp’s output in light of any variations in your power amplifier’s impedance.
- Before the music signal leaves the Rhythm 1.1, it is compared with the output of the tubes – and immediately corrected to match the tubes at their ouput.
- This corrects the signal if it has been affected by inductance or capacitance of the interconnects leading to your power amplifier.
- It also corrects the signal for any variations introduced by the music signal’s effect on your power amplifier’s impedance.
No Cathode Follower: Many tubed preamps use an extra tubed circuit after the gain stage, called a cathode follower. This circuit is intended to lower the preamp’s output impedance. Because a cathode follower can impair the accuracy of a preamp’s dynamics, the Rhythm 1.1 gets this done without one.
This last bit means that the output impedance is a relatively high 434Ω, but with modern amps, this shouldn’t be an issue. With a TKD volume pot and balance controls, the pre also is single-ended only, and yes, that’s by design. It also features a mono switch and a tape loop.
Shown here with TAD CR-1 loudspeakers, Odyssey Audio mono amplifiers, the new ($6,500) Veros One phono pre from LKV Research, a Vinyl One from Art Audio and cables from Luminous Audio. The Marantz NA-11S1 sat in as a digital multi-source, opposite a VPI Classic 3 turntable with a Dynavector XX-2 cartridge.
During my visit, they were between stuff, so I didn’t really get a chance to settle in for a long visit. What I did hear was engaging, and I indulged a little grin, thinking that of all the times I’ve heard the magnificent TAD stand-mounts, the best of these featured tubes and vinyl in the chain. Must be something there [wink, wink].